1. Field of the Invention
The present invention relates to a brake-transmission shift interlock device for an automatic transmission system and more particularly, to a device that includes a solenoid having a two part plunger with an exterior second portion of the plunger positioned to prevent movement of a transmission member thereby preventing operation of the transmission shifter until the brake is depressed.
2. Background of the Prior Art
Automatic transmissions are commonly used for controlling the modes of operation of an automobile including park, drive, reverse and neutral. The modes of operation are selected by moving a shifter, integrally mounted to the automatic transmission, to a position corresponding to the indicated mode. These modes of operation have simplified a driver""s task when operating an automobile. However, experience has shown that it is possible for an automatic transmission to xe2x80x9cslipxe2x80x9d from a park mode to a drive mode without the driver moving the shifter, thereby compromising safety and possibly developing into a collision involving the automobile and an adjacent structure.
A well-known method in the art of correcting aforementioned problem is to employ an interlock device that allows the automatic transmission shifter to move from the park mode only when the automobile engine is running and the brake pedal is depressed. The interlock also allows the shifter to be moved back to the park mode irrespective of the shifter positions.
A well-known interlock device that accomplishes the above objective utilizes a solenoid such that when in a de-energized state, prevents movement of the transmission shifter, and when energized (by depressing the brake pedal) allows the shifter to move from the park position. To minimize the required lineal force to operate the solenoid thereby reducing the size of the solenoid, the solenoid was designed such that the travel of an internal plunger component of the solenoid, occurred in a horizontal line to minimize the effects of gravity on the plunger.
Although effective in correcting the above-stated problem, prior art interlocking devices were required to use relatively large solenoids to provide sufficient lineal force to overcome the binding of internal solenoid components caused by an external xe2x80x9cblockingxe2x80x9d component joined to a plunger component of the solenoid. The blocking component being utilized to impede the travel of a preselected transmission member thereby preventing operation of the transmission. These relatively large solenoids generate undesirable noise when operated and use components that xe2x80x9cwear downxe2x80x9d relatively quick. Examples of prior art designs are illustrated in U.S. Pat. Nos. 5,379,872; 5,309,744; 5,293,763; 5,150,593; 5,036,962; 4,983,960; 4,638,279; and 1,768,518.
Therefore, a solenoid operated interlocking device is required that has less binding between internal solenoid components, requires less lineal force to operate, is relatively smaller in size and generates less noise than the prior art solenoids.
It is an object of the present invention to overcome many of the disadvantages associated with brake-transmission shift interlock devices for automatic transmission systems that employ solenoids to prevent operation of the transmission.
A principle object o the present invention is to provide a device that prevents an automatic transmission shifter from being moved from the park position unless the brake pedal is depressed. A feature of the device is a solenoid operator having relatively xe2x80x9csmallxe2x80x9d dimension to remove an obstruction to the movement of a transmission member. An advantage of the device is the relative xe2x80x9cnoise-freexe2x80x9d operation of the solenoid.
Another object of the present invention is to reduce the binding between components of the solenoid. A feature of the device is a two piece plunger component of the solenoid. An advantage of the device is the reduced binding between plunger and bobbin components of the solenoid.
Yet another object of the present invention is to reduce the lineal force required to operate the solenoid. A feature of the device is an axial offset plunger portion (in relation to a horizontal longitudinal axis of the solenoid) obstructing movement of a transmission member. An advantage of the device is the reduction of solenoid size and the corresponding reduction of power draw.
Yet another object of the present invention is to secure electrical conductors supplying power to the device. A feature of the device is a force fit of the conductors into apertures, and the securing of the conductors in the apertures by a pair of ribs that receive an edge portion of the enclosure receiving the conductors. An advantage of the device is the strain relief of the conductors at the enclosure entrance caused by movement of the device during transmission shifter operation.
Another object of the present invention is to limit wear on a component 5 supporting a plunger portion blocking a transmission member. A feature of the device is a sleeve insert in a plunger support. An advantage of the device is increased service time and a corresponding decrease in solenoid repair.
Still another object of the invention is a limited supply voltage range. A feature of the device is a voltage regulating circuit board that supplies power to the solenoid coil. An advantage of the device is that a smaller coil design and corresponding smaller solenoid is required to operate the device in extreme temperature ranges.
Briefly, the invention provides a brake interrupt device for an automatic transmission system comprising a support member, a solenoid secured to said 15 support member, said solenoid including a plunger member; means for moving said plunger member from a first position to a second position; means for moving said plunger member from said second position to said first position; means for preventing movement of an automatic transmission shifter; and means for preventing binding of said plunger thereby allowing movement of said plunger from said first position to said second position.